Here is the AnyRail file for the layout JEM. I enjoy AnyRail for its ease in making new layouts and the nice appearance that you can obtain.
The outside O-60 loop is just over 37 feet long. With two 8-foot trains, the separation would be 10'7" between trains. So two short trains could be run at the same time on the outside loop using command control of some type (LionChief, Legacy,DCS). This would allow three trains & engineers running and routing through the two loops of the layout (with a fourth 8-foot train as visible staging on the long siding). That looks like some fun!